Method and apparatus for making grease



Aug. 16, 1949. I G. M. HAlN 2,478,917

METHOD AND APPARATUS FOR MAKING GREASE Filed Sept. 24, 1946 5Sheets-Sheet l INVENTOR. G EORGE M. HAIN BY W ATTORNEY Au 16, 1949. G.M. HAlN 2,478,917

METHOD AND APPARATUS FOR MAKING GREASE Filed Sept. 24, 1946 3Sheets-Sheet 5 INVENTOR. GEORGE M. HAIN ATTORNEY Patented Aug. 16, 1949METHOD AND APPARATUS FOR MAKING GREASE George M. Hain, United StatesNavy Application September 24, 1946, Serial No. 699,068

6 Claims.

(Granted This invention relates to a method and apparatus for themanufacture of high quality greases by a continuous flow process.

The art of manufacturing high quality greases is recognized as a highlyspecialized phase of lubrication chemistry and is fraught with numerousdifficulties. The control of sensitive variables must be closelymaintained in order that operating conditions can be changed rapidly andaccurately.

Continuous processes for grease manufacture generally include thesuccessive steps of heating an intimately mixed slurry of prepared soapin a mineral oil or other base fluid medium to achieve complete solutionof the soap therein, the sudden cooling of the solution thus obtained toform a gel, and the mechanical working of the gel to a greaseconsistency. Heretofore, both the apparatus and methods employed in suchprocesses have in general proven unsatisfactory when applied to qualitygrease manufacture.

High-quality greases ar critical compositions comprising essentiallyloosely flocculated dispersions of tiny soap crystals in a fluid medium,the size and state of aggregation of the crystals having a pronouncedeffect on the physical properties of the finished grease. Amicrocrystalline soap structure of large inter-crystalline surface areais necessary in such a grease to hold the fluid phase in equilibrium andprevent its bleeding from the mass. However, none of the knowncontinuous or semi-continuous processes for making greases are operativeto produce the optimum microcrystalline dispersion of soap.

In the preparation of many greases having the desired microcrystallinesoap structure, the transition from hot fluid to stable gel must beaccomplished as quickly as possible, since slow cooling promotes crystalgrowth and therefore less interfacial area to hold the fluid. As an aidto the desirable rapid transition, the heating step should not becarried to a temperature materially beyond that needed to completesolution of the soap in the base fluid. Further, the cooling shouldproceed to equilibrium conditions at such a rate as to avoid theformation of coarse soap granules.

Accordingly, it is an object of my invention to provide a method andapparatus for the manufacture of high quality greases, such as lithiumsoap greases, by a continuous process which affords complete control ofoperating conditions at all stages.

Another object of my invention is to provide under the act of March 3,amended April 30, 1928; 370 '0. G.

a method and apparatus for the continuous manufacture of greases whichmethod and apparatus create a condition whereby the grease is subjectedto internal working in several successive stages. 7

It is another object of my invention to provide a continuous flow methodand apparatus by which it is possible to convert a fluid greaseformulation into a stable grease characterized by its stability andhomogeneity,

Another object of my invention is to provide a simple apparatus for thecontinuous manufacture of high quality greases, which apparatus ischaracterized by its having a restricted cross section in its heatingand cooling sections.

It is another object of my invention to provide an apparatus havingheating and cooling sections wherein essentially film type heat transferoccurs and heating and cooling of the composition occurs at very rapidrates.

Further and more specific objects will in part be obvious and in partappear hereinafter.

My invention, accordingly, comprises the process of making high qualitygreases in continuous flow manner, which process includes the severalsteps and the relationship of one or more of such steps to each of theothers, and the apparatus comprising successive mixing, heating,cooling, and working sections which possess the features of constructionand combinations of elements exemplified in the following detaileddisclosure. The scope of the invention will be indicated in the appendedclaims.

The process is carried out by preparing a fluid grease formulation whichconsists of the fluid base for the grease having suspended therein thesoap thickener, a typical one of which is lithium stearate, and variousbalancing ingredients such as oiliness, oxidation inhibiting, rustinhibiting additives and the like as may be required in the final greaseformulation. The fluid formulation is conducted through successiveheating and cooling steps in a continuous flow method in essentiallyfilm form, so that the heating and cooling are characterized by beingcarried out as film heating and cooling heat transfer operations. Ratherthan heating and cooling a single large mass of fluid in a vat orconduit, a continuously flowing fluid having a cross section of theorder of the thickness of a flowing film of the base fluid is subjectedto the heating and cooling operations.

The apparatus in which the process is carried out is characterized bystructure which maintains the flowing, fluid, grease formulation in theform of a fast moving film. It is further charcoil 38, water beingintroduced through the inlet acterized by being made up of smalldiameter 40, allowed to pass over and around the coil and thin-walledconduits in which the largest diam leave through the outlet 4 I. Thisdischarge end ter is of the order of twice the thickness of a. of thecooling section is connected by a lead free flowing filmoi the basefluid, By employ- 5 througha alved; to a variable spe ear Dump ingsauch' restricted diameter throughout, and 43, Near this valve junctionand alsoat the dismaintaining a high velocity of flow of the film charge(and 6f the 'pump 33 are connected other through the conduits, a precisecontrol is main; sampling tubes 44 and 45, A pressure gage 57 i tainedat a times Over the temperature of the 'aiso connected at the dischargeend of this pump fluid, and in addition, the fiuid pagftj l la jb, i 10which end is joined to the working section the the Cooling S a e Wh t isConverted to l; construction of which will be fully described hereis subec ed o internal shearing res whic inafter in connection with Figure 3.One end of imp t o t a Certain amellnt O'f Work during" a T junction 49is connected to the discharge the thermal treatment qqitiQQfiHYe s i vie oftheworking section, the other two ends ity of flow of the fluidthrough the heating e 15 being connected respectively through a valvecooling sections is matched to the heating 'cap'ac- 50 td a {iacuumizjngSystem 5 and through a ity and the cooling eapacityof h p atus, so i e1- 52' to the-intake oi the gear pump as. lien is Closely Within fewdegrees of the 013171 valve 53 controls the flow of finished grease intot ct m v 20 the take-ofi tube 54 to th of e. Fiuie 2' 'th s n w l, 1rent 6i [e the O QL l e le i disclosure when taken in conjunction withthe aceomp n ng/ draw h i ,i a

Ffgufel. a c 'd "gram o'fan appa- 9 v diagram of a second 11 aracerlstic "Sft'he un ,7 A int .@ie 1ii iii 513. t. e em i the ho p WH m elWQ JIQF IFQ 'PL hi h r ei l e eaa i. vT o; heheatin ube describedequivalent to t noeene i'ef ib fi u e. l. r u hfiaet aielt ilower eldiiw t tafl maiyri pqrii ns g hi 1 1; as he. he t ng P SU-ISLPBQQ; 8-.,.-Th tubes 68 are enclosed in a c insu ating material 68.v The tubesare elecifiurupQ ll. P? e Q eri 9 1 MW w I M t on 29. Jhaheat eaiin ffli ubal-t IL-5 E unitislmas of; t

ap eiatee by o. q he ii e eetimi -s5. olui qe; is die-eh re s under. weeux fr m; heh a ine tui esnt aiheaiier .1 br uehlhi hit 1S @0 9 ed eanoherh adsi p u a ty :.QQ mbes 1?. hav nethe, sameed mehs ou :aeth -h aina tubes- Eac i fs he-p i ne be eie r asedm ialr r r ieual.Water-Jacket. lei-wh ch. sfitted; w h; a wa e ein et and azwat ncutlet8L Jlfhewt in e me rom a condu t-. .i f out: lets 8i discharge into thepther conduit the w t m ly ystem. The, grea ecpmppsition d sch ed. fom; the Q o'f a bea. intoeth heaqe iilii n i ediu h arnum 5 and: edi ethee orkine; vic Bi vv Fi mers rti s 9i hafin shedi rea i mp t (m e kenfi een ian yo t9 thei e ntaelee h h-ea i e ballz hec valve"e ewhil ethel r eor of anewlee. through the .ela b e 8$ to e ,ls rsiisfliimime i bcr y a 'B i the apparatus is placed in operatiom itiniaj lbe evac uatedthro eh a valve e10 which connects to umpe l 1 t bi in 'thee qq ael ceais, o he am? aresids I w larg'id ialn iie s meatoneenaatsioe cap 31which hole through its; ce r 1ter, and atjheot plurality of smallperforations over a central portionof a diameter matching the inlet issandrwiched between the fiat surfaces of the flanges, gasketed, andsecured firmly by the bolts 94 which pass through the plate and flangesand join the top and bottom sections. The fluid conduits of theapparatus may be used to connect the working means with the pump 43shown in Figure 1.

With reference to Figure 1, in preparation for starting, the system isevacuated by means of any convenient pumping equipment 5i. When asubstantial reduction of the air pressure in the system has beenaccomplished, valve 50 is closed and the cold slurry of soap and fluid,which has been maintained in a free-flowing state by means of themechanical stirring apparatus, is pumped at a pressure of about 800pounds per square inch into the narrow diameter tubing of the heatingcoil. Here, the accurate control afforded by the unique form of heatingapparatus employed permits attainment of complete solution of the soapcrystals in the base fluid medium just as the fluid is discharged fromthe heating coil. This hot solution enters the cooling coil underpressure where it is transformed quickly into a semi-rigid gel, whichgel in its forced passage through the cooling coil is worked at leastpartially to a grease consistency by the severe shearing stresses set upin the narrow diameter tubing comprising the coil.

The rapid succession of heating and cooling steps occurring in theheating and cooling sections of the apparatus minimizes fire hazards andthe possibility of oxidation of the hot fluid base and also avoidsdamage to the soap particles and additives in the composition. The rateof flow through the narrow diameter heating section is adjusted so thatthe total time of heating does not materially exceed about 15 secondswhen a fluid is brought from an ambient temperature of about 70 F. to amaximum temperature of discharge from the heating section of about 480or 500 F. The exact velocity of flow through the heating and coolingsections therefore will be fixed by the dimensions of the apparatus andthe specific physical properties of the base fluid which fix thosedimensions but will roughly approximate about 50 cubic centimeters perminute in a tube having a diameter of about one-quarter of an inch.

The cool, partially worked grease composition is picked up by the gearpump 43 shown in Figure 1 and pumped into the working section where itis worked to the consistency of a finished grease by being extrudedthrough the finely perforated plate. The grease first passing theworking section is recycled into the gear pump until the plumbingassociated with this pump and the working means has been filled withgrease and a head of grease has been built up sufficient to activate thepreset ball back valve 53. Then, as grease continues to be forced out ofthe working means, which acts also as a reservoir for grease, a fixedminor portion is constantly taken off through the ball check valve asthe finished product. The remaining rease is recycled into the pum andworking section. By this method of constantly taking off only a smallportion of finished grease and recycling the remaining portion, it willbe apparent that each individual portion of finished grease has had atleast several passes through the perforated plate of the workingsection.

During the process of manufacture, the occlusion of air to formdetrimental pockets in the finished grease is substantially entirelyprevented because of the high pressures employed, and the extensiveworking to which the grease is subjected.

Instead of employing the more or less conventional steam orwater-jacketed pipe-still heating coils set in a furnace heated by coal,gas or oil fires, metal tubing, and preferably corrosion resistantstainless steel tubing, of very small diameter and wall thickness isemployed and heated by an electric current. As seen from Figure l, thetubing is electrically connected across the secondary terminals of thepower transformer 33. The current flowing through the tubing when theprimary circuit of the transformer is energized produces heat at asteady even rate over the entire length of the coil. The rheostat 34inserted in series with the primary windings of the transformer governsthe amount of current flowing there and hence, :by normal transformeraction, governs the amountof current induced in the secondary windingsand flowing through the heating section. The rheostat thus serves as aneffective and accurate temperature control of the heating means. Becausethe heat is generated directly and evenly in the tubing walls, andbecause the tubing is of such narrow diameter, substantiallyinstantaneous heat transfer is obtained. Furthermore, local overheatingor variations in rate of heating, both of which are detrimental to theattainment of good grease structure, can be avoided. Since any givenslurry is flowing through the heating section at a rate fixed by thepumping means employed, it is practicable to regulate the heating sothat the temperature needed for complete solution of the soap in thefluid medium may be reached close to the discharge end of the coil andnot be exceeded to any appreciable degree. As stated above, thistemperature may for certain soaps be as high as from about 480 F. toabout 500 F.; but in general it will be slightly above 300 F.

Substantially instantaneous heat exchange is also afforded in thecooling section by virture of the employment of narrow diameterthin-wall tubing in its construction. It will be recognized by thoseskilled in the art that this point of control is very important withregard to the quality of grease produced. The solution must be cooled sorapidly that the fine soap crystals which precipitate and form the basisof a gel structure do not have time before equilibrium is reached togrow or agglomerate into the relatively large soap granules which permitthe final grease composition to bleed. Furthermore, the solution must becooled at the same rate throughout in order to produce a gel structurewhich is homogeneous D throughout.

My unique cooling means affords the operational control necessary to theaccomplishment of these ends. In addition, it provides a means of atleast partially working the semi-rigid gel to a proper greaseconsistency. As the gel is formed in the narrow diameter coolingsection, it is forced rapidly through the tubing and tangentiallyagainst the inner walls thereof at high rates of shear. The gelstructure is partially broken down to produce a composition which onleaving the cooling section has a grease texture. More extensive workingof the grease takes place in the working section of the apparatus.

Because of the high operating pressures and the narrow diameter systememployed in this continuous flow method of grease manufacture I haveattained what is essentially a self working system which develops highrates of shear substantially throughout. In the working section theshearing stresses are magnified greatly as the grease compositionsforced tlirou'ghthe tiiiyholes at the" perforated plate.-

- In describing the heating and'cooling sections of the apparatus,reference was" made to maintaihing a narrow diameter throughout thesetwo sections preferably in the form of a narrow diameter tube which'createda condition offiow-in the apparatus which-I" chose to callaforced-film new. The exact dimensions of the tube, that is, the tubediameter, are not critical but Shoilldbe of'the order of about two thefree-flowing film of the base fluid and terraces greasefiuids this isless than one-half orthree eighths of an inch;

h To simplify a description of my apparatus and the operation thereof Ihave hitherto'spoken of a slurry as comprising merely a mixture of soapcrystals ma base fluid medium It is to be understood that inaddition tothe soap and base fluid constituents there may be present in the slurryany of the common balancing ingredients Suchas oxidation and corrosioninhibitors; oiliness and extreme pressure'additives, and polymerthickeners.

'Ihe-particular-soap and other additives are, in general, blended withthe base fluid prior to its introduction into the apparatus. In otherwords, it is preferred that the compounding of the ingredients;including any necessary, chemical reactions, occurs outside theapparatus Using the apparatus described, and following the methodsdescribed, instrument greases of I high quality having various types ofbase fluids have been prepared by my continuous-process at a rate ofabout 120 pounds greases were all characterized by their being smoothhomogeneous mixtures of abase fluid lubricant-with a'metallic soap and,when appro priate, various balancing ingredients. Various diestersand'othe'r synthetic fluids such as the silicones, hydrocarbon fluidsand polyethylene'oxide fluids were used as base fluids; The dispersionsof the-soap in the grease in all cases werenomm gene'cus and noobjectionable base fluid sepaw tions occured even after months ofstanding in many'cases. Typical formulations which were prepared by theabove methods and in the'above' d'escribed'apparatus are shown below inthe't'abie.

times the thickness of per 8 hour day; The i terials thereby introducinga desirable factor of:

Aeration of the grease produced with the resale ant decrease in qualityand'in'creasedtendency to bleed is'prcven'ted by using sures throughoutthe system;

' lit-will be apparent that manymodifications maybe made in my'inventionWithout departing from the scopethereoi= Accordingly, it'i's desiredthat the present disclosure be construed as illus--- trative tion. r r YThe'inven'tion described herein maybe manufactured and usedb'y or forthe Government of of myinventio'n and not by way oilimitathe UnitedStates of'America for governmental- .p'unp'oses without the payment ofany royalties thereon or therefor;

What is claimed is:

1; Apparatus for the continuous preparation of grease comprising aslurry mixing tank, a dis charge conduit from said tank, a-high pressurepump connected to said discharge conduit, a grease heating conduitconnected to and electrically insulated from said high pressure pump,

an electrical heating circuit connected through said grease heatingconduit, a heat insulating medium surrounding'said grease heating conduit, a grease cooling conduit connected to and electrically insulatedfrom said grease'heating conduit, a cooling medium conducting jacketenveloping said grease cooling conduit, said heati {and said coolingconduits each being of a a; meter substantially twice the thickness of afree-flowing film or the base fluid of the slurry, asecond high pressurepump connected to the discharge side of said grease cooling conduit, agrease Working section connected to the discharge side of said secondhigh pressure pump, said grease working section including a finelyperforated membrane through which the grease is forced, and check valvedmeans connected to said grease working section.

charge conduitfrom said tank, a high pressure Table V I Parts A.S.T.M.WgtPer No.- Components ,by; Pcnetra- 7 Cent Evan} Wgt. tion- Bleedingration 2.. 4t cjrtiary-butyI-Q-Dhcnyl-phcnol 0.2 245 2 0.33'

(I -Z-ethylheXyl sebacat 34.8 di-Z-cthylhexyl adipate 52.0

. lithium stcaratefl nfl 14.0 I 4-tertiary-butyI-2-pllenyl-ph 0,2 7 v- H3 sorbitan monoolcate 29 260 3.90 0.98

'polybutene (MW IZUOO). 1.0 did-ethylhexyl scbacateuens .i 82.8

My inventionlthuslprovidesza unique method and apparatus for thecontinuous manufacture of high quality" greases, whichzmethod ischaracterized by being: a continuous :process of forced-fi-lm-flow whichworks the grease-composition in all stages o'f-=its;rnanufacture.. Theap= paratus 'is correspondingly, a narrow diameter, self working', self=scraping system'inwhich high rates of shear within the composition areobtained. It alfordsi closecontrol of operational variables, and reducesthe handling of raw mag pump connected to said discharge conduit,.agrease heating conduit connected. to and electrically insulated fromsaid high pressure pump, an electrical heating circuit connected throughsaid grease heating conduit, aheat insulating medium surroundingsaidigre'ase heating con-- duit, a grease cooling conduit connectedtoand electrically insulated from said grease heating conduit, a coolingmedium conducting jacket enveloping said grease cooling conduit, saidheat ing and said cooling conduits each being of a high Working presgrease discharge 2; Apparatus for the continuous preparation of greasecomprising-a slurry mixing tank, a dis diameter substantially twice thethickness of a free-flowing film of the base fluid of the slurry, asecond high pressure pump connected to the discharge side of said greasecooling conduit, a grease working section connected to the dischargeside of said second high pressure pump, said grease working sectionincluding a finely perforated membrane through which the grease isforced, a recycling connection between the entrance and discharge sidesof said grease work section, and check valved grease discharge meansconnected to said grease working section.

3. Apparatus for the continuous preparation of grease comprising aslurry mixing tank, a discharge conduit from said tank, a high pressurepump connected to said discharge conduit, a header connected to saidhigh pressure pump, a second header, grease heating means connectedbetween and electrically insulated from said headers, said greaseheating means comprising a plurality of individual grease heatingconduits and an insulating medium through which said grease heatingconduits extend, an electrical heating circuit connected through each ofsaid heating conduits in series, a conduit from said second header to athird header, a plurality of grease cooling conduits connecting saidthird header to a fourth header, individual cooling medium conductingjackets enveloping each of said grease cooling conduits, said heatingand said cooling conduits each being of a diameter substantially twicethe thickness of a free-flowing film of the base fluid of the slurry, asecond high pressure pump connected to the discharge side of said fourthheader, a grease working section connected to the discharge side of saidsecond high pressure pump, said grease working section including afinely perforated medium through which the grease is forced, and checkvalved grease discharge means connected to said grease working section.

4. Apparatus for continuous preparation of grease comprising a slurrymixing tank, a discharge conduit from said tank, a high pressure pumpconnected to said discharge conduit, a header connected to said highpressure pump, a second header, grease heating means connected betweenand electrically insulated from said headers, said grease heating meanscomprising a plurality of individual grease heating conduits and aninsulating medium through which said grease heating conduits extend, anelectrical heating circuit connected through each of said heatingconduits in series, a conduit from said second header to a third header,a plurality of grease cooling conduits connecting said third header to afourth header, individual cooling medium conducting jackets envelopingeach of said grease cooling conduits, said heating and said coolingconduits each being of a diameter substantially twice the thickness of afreeflowing film of the base fluid of the slurry, a second high pressurepump connected to the discharge side of said fourth header, a greaseworking section connected to the discharge side of said second highpressure pump, said grease working section including a finely perforatedmembrane through which the grease is forced, a recycling connectionbetween the entrance and discharge sides of said grease work section,and check valved grease discharge means connected to said grease workingsection.

5. Apparatus for the continuous preparation of grease, comprising, aslurry mixing tank provided with a discharge conduit, a high pressurepump connected with said discharge conduit, a heating conduit connectedto and electrically insulated from said high pressure pump, means forpassing electric current through said heating conduit, a cooling conduitprovided with a cooling medium conducting jacket and connected to saidheating conduit and electrically insulated therefrom, said heating andcooling conduits being of a diameter not greater than approximatelyonehalf inch, a second high pressure pump connected to the dischargeside of said grease cooling conduit, and a grease working sectionincluding a finely perforated membrane through which the grease isforced connected to the discharge side of said second pump.

6. Apparatus of the type defined in claim 5 wherein the worker sectioncomprises two substantially symmetrical axially apertured flange membersaxially aligned with each other, a thin perforated metal platepositioned between the faces of said member in gasketed relationtherewith and extending across said axial apertures, and bolt meansholding said flange members in rigid, face-to-face relationship.

GEORGE M. HAIN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,019,413 Batchelder Mar. 5, 19121,175,470 Perkins Mar. 14, 1915 2,257,945 Fraser Oct. 7, 1941 2,339,873Morway et a1 Jan. 25, 1944 2,372,052 Beerbower et al Mar. 20, 19452,406,655 Bax et al Aug. 27, 1946 2,433,636 Thurman Dec. 30, 1947

